Surface contactor for blast cleaning machine



April 15, 1958 H. HASTRUP ET AL 2,330,403

SURFACE CONTACTOR F OR BLAST CLEANING MACHINE Filed Dec 27, 1955 FIE] INVENTOR. HERMAN HASTRUP ROLF C. HASTRUP ATTORNEY United States Patent SURFACE CONTACTOR FOR BLAST CLEANING MACHINE Herman Hastrup, Kaneohe, Oahu, Territory of Hawaii, and Rolf C. Hastrup, Torrance, Calif.

Application December 27, 1955, Serial No. 555,495

3 Claims. (CI. 51-11) This invention relates to grit blasting apparatus for cleaning surfaces, in which apparatus there is directed from a nozzle toward said surface a stream of air and abrasive material and from which surface the spent abrasive and debris are withdrawn in a stream of air through a confined passageway, said nozzle and said passageway being positioned in a housing generally termed a nozzle head or operating head. More particularly it relates to a surface contactor device adapted to contact an area of surface being cleaned and to serve as a connecting means between said nozzle head and said area of surface.

In abrasive blasting machines of the type above referred to in which there are employed confined air streams, one directed toward and the other away from the area of surface being cleaned, an object sought is to conduct the blast cleaning operation without any spattering of the abrasive material outwardly from the area of impingement, and to keep all abrasive, dust and debris confined-in other words to provide an operation that is completely clean and therefore subjects neither surrounding fixtures nor the clothes of the operator to dirt or dust. The operation is adapted for indoor work and to the surfaces of objects of varying size, including relatively small objects.

To conduct such an operation it is necessary that the surface contactor do more than simply contact the surface to be cleaned. It must encircle and confine an area of said surface which is immediately undergoing being cleaned, and it should effectively enclose and seal off the space between the nozzle head and said area of surface, within which space the blast stream impinges against said area and the suction stream picks up the spent abrasive and debris and draws them away from said area. It is therefore desirable that the surface contactor be non-air pervious so that there may be no leakage of abrasive or dust to the surrounding space and no leakage of air from the outside into the blast area, either through the material comprising said surface contactor or underneath the edge of the surface contactor.

In U. S. Patent #2,723,498 issued November 15, 1955, to Herman Hastrup and Dale F. Pinkerton, and in our Serial No. 521,719 filed July 13, 1955, there are described portable blast cleaning machines of the type hereinabove referred to and having non-air pervious surface contactors, the material comprising said contactors being generally continuous or in one piece. Because of the irregularity of the surfaces encountered on many objects to be cleaned, difliculty is frequently encountered in maintaining a seal between the edge of the contactor and the surface being cleaned when the enveloping wall or skirt of the contactor is in one continuous piece.

It is an object of this invention to provide a non-air pervious surface contactor for abrasive blast cleaning machines of the above described type which permit of substantially complete contact against irregular surfaces along the entire circumferential boundary line of the immediate working area of the surface undergoing treat- See ment to substantially seal said area and the space between the nozzle head of said machine and said area of surface against the passage of dust or abrasive to the surrounding space or the infiltration of air from the surrounding space.

Other objects and advantages of the invention will appear from the ensuing description and the appended claims.

One form of the invention is illustrated by way of example in the accompanying drawings and is described in detail hereinafter. The particular constructions herein shown and described are to be construed as illustrative only, and not as limiting the invention.

In the drawings:

Fig. l is a longitudinal sectional view of a preferred form of our surface contactor shown in place on the nozzle head of an abrasive blasting machine of the type above referred to, a fragmentary sectional view of said nozzle head being shown;

Fig. 2 is a bottom plan view of the device shown in Fig. 1.

Referring to the drawings, a cylindrical outer casing 10 and an inner casing 11, spaced apart from said outer casing, form an inner channel 12 and an outer channel 13 at the outer end (toward the surface to be cleaned) of the nozzle head of an abrasive blast cleaning machine of the type wherein abrasive is directed, by an air stream, through said inner channel toward a working area of the surface being cleaned and spent abrasive is drawn away from said working area by a suction air stream through said outer channel. The outer casing 10 extends axially outwardly beyond the end of said inner tube to form a rim 15. Preferably, said casings 10 and 11 are made of abrasion resistant rubber and may be molded with spaced, web members 16 (Fig. 2) positioned radially between said inner and outer casings and integral with the walls thereof to give stiffness to said casings. The wall of the outer casing 10, at and near said rim 15, is desirably of increased thickness to give adequate strength for the attachment thereto of the surface contactor, generally designated as 17.

Coming now to the surface contactor, a metal sleeve 18, adapted to snap over the rim 15 of the outer casing 10, fits into a recess 19 in the outer face of casing 10. Several laminae of rubber or similarly resilient material, 20 (three such laminae being shown in the drawings), are positioned around the said sleeve 18' and may be clamped there against by a suitable outer band 21. Other means may be employed to secure said laminae around said outer casing 10, such for example as by vulcanizing or otherwise bonding the laminae to a collar of suitable material, which said collar may then be suitably fitted around the outer end of casing 10. The said laminae completely surround the outer casing 10 and are of suflicient width that they extend a substantial distance axially beyond the end of said casing to form a curtain or skirt which completely encircles and envelopes the space immediately beyond the end of said outer casing 10. That portion of each lamina which extends beyond its attachment to said outer casing 10 is slitted axially a substantial distance from its outer edge to form a multiplicity of flaps 22. The flaps are so arranged that those in any given lamina overlap by a substantial distance the joints formed by the edges which face each other of flaps in adjacent laminae. Thus, due to the flexibility and resilience of the individual flaps, the multiplicity thereof and the joint breaking feature, when the surface contactor 17 is applied to an irregular surface being cleaned, the segmented laminae effectively seal off the working area of said surface and the space between the end of the nozzle head and said surface both from leakage of dust and abrasive to the'surrounding space and from leakage of air from the outside into the blast area.

The number of laminae employed may-vary depending upon their thickness, the flexibility and resilience of the material of which they are made, their thickness, the width of the flaps, the shape and size; of their crosssection, and the like. With flaps which are relatively narrow it is desirable that a greater number of laminae be employed than when the flaps are of greater relative width. The flaps should have sufiicient surface area that when the surface contactor 17 is held against an irregular surface so that the flaps are distorted from their normal position the area of surface contact between flaps is efiective to seal the contactor against the passage of air either 'outwardly'or inwardly therethrough. The, outer ends of the laminae 20, which together form the mouth of the contactor, need not all lie in the same 1 plane; nor need the outer edge or mouth of the contactor lie in the same plane. When desired the mouth may be either convex or concave and may be made to conformto square corners or rounded surfaces. Surface .contactors with different shaped mouths, and with the shape and dimensions of the flaps varying to some degree from each other, may if desired be made for use with surfaces of varying degrees of irregularity. One such contactor may be unclamped or otherwise readily removed from the nozzle head and another applied when the variation in surface irregularity. makes such desirable.

While we have shown a preferred form of our inven tion, it is to be understood that Various changes may be made in its construction without departing. from the spirit of the invention as defined in the appended claims.

We claim:

1. In an abrasive blast cleaning machine, an operating head provided with a channel through which a blast stream is directed toward a work surface and a separate channel through which a suction stream draws spent abrasive away from said surface, said operating head being provided with a surface contactor for contacting said working surface to encircle and confine an area of said surface being cleaned, said contactor enveloping the space, between said operating head and said area of surface, within which the said blast stream impinges against said area and the said suction stream draws the spent abrasive away from said surface, said surface contactor comprising a plurality of laminae of flexible, resilient material constituting a composite of ring-like members unsecured to'each other throughout a substantial part of their lower widths, the upper end of said members being secured to the outer end of said operating head and their lower edges being approximately even with each other to provide askirt about said space between said operating head and said area of surface, and each lamina being slitted axially a substantial distance from its unsecured edge to provide a multiplicity of flat axially extending flaps, the adjacent flaps in each of said laminae having the edges thereof in abutting relation and the slits therebetween overlapped by flaps in another lamina to render said skirt substantially impervious to the passage of air from the surrounding space into the blast area and from the blast area into the surrounding space.

2. The deviceof claim 1 in which said resilient material is rubber.

3. The device of claim 1 in which the laminae at one end are bonded together and secured to a collar which is secured around said operating head.

References Cited in the file of this patent UNITED STATES PATENTS 2,455,514 Mead Dec. 7, 1948 2,494,773 Mead et a1. Jan. 17, 1950 2,723,498 Hastrup et al Nov. 15, 1955 

